Women's greater ability to detect odours and aromas could be linked to the oestrogen hormone, according to research.

A US study showed women of reproductive age are far better at identifying odours than men after repeated exposure to the source of the smell.

Researchers found female subjects whose odour sensitivity was tested many times, were able to detect the cherry-almond smell of benzaldehyde and a few other odours at progressively much lower concentrations.

Male subjects taking part in similar tests never improved their ability to identify odours with experience.

Some studies have shown that during ovulation, there's a surge of oestrogen which increases sensitivity

Professor Tim Jacobs, Cardiff University

Researchers suggest the study results raise the possibility that female sex hormones have a role in enabling exposure-induced increases in odour sensitivity.

Experts say many studies show women out perform men in olfactory (sense of smell) sensitivity.

Tim Jacobs, Professor of Physiology at Cardiff University, said: "Some studies have shown that during ovulation, there's a surge of oestrogen which increases sensitivity.

"The structure of the nose is the same in women as men.

"They don't have any more receptors in the nose.

"Studies have also shown smells activate a greater region in the brain in women than men."

Psychologist Neil Martin says the study findings are interesting.

Female 'superiority'

He said: "There is a wealth of scientific data showing women's superiority at identifying and detecting odours at even very small concentrations.

"A recent study showed that although sex differences in olfactory superiority are not found in middle age and beyond (45-87 years), personality and semantic memory were found to be better predictors of odour identification, even when sex, age and education were taken into account."

The tests were originally carried out on six subjects.

The same six subjects took part in a second test alongside six new subjects.

They used benzaldehyde again and a second substance, isoamyl acetate, which smells like bananas.

Sensitivity to benzaldehyde increased substantially for both the experienced women and the new "naive" group, but not for men.

However this was not repeated with isoamyl acetate.

Scientists at Monell Chemical Senses Center concluded the effect of repeated testing of odours was replicable but odour specific.

The tests were then carried out in young girls and post menopausal women to assess whether hormones played a part.

An equal number of age-matched boys and men were also tested.

Among the younger subjects, sensitivity to benzaldehyde did not change with time for either boys or girls.

Similarly, there were no significant gender differences across the older groups.